Study Design. Sensory innervation of the lumbar dura mater passing through
the sympathetic trunk was investigated by neuronal tracing and immunohistoc
hemical methods.
Objective. To assess an anatomic basis indicating that sympathetic block in
the higher lumbar region is effective for patients with low back pain.
Summary of Background Data. Low back pain is elicited by disorder or mechan
ical stimulation of the lumbar dura mater. Clinically, the authors often ha
ve observed patients in whom root block at the responsible level or sympath
etic block at the higher level could relieve low back pain. Therefore, ther
e may be two different sensory routes, the segmental innervation at the sam
e level and nonsegmental fibers from higher dorsal root ganglia.
Methods. The tracers were injected into the sympathetic trunk between L3 an
d L4 of rats. The lumbar dorsal root ganglia and dura mater were examined,
and labeled cells were measured in size and the distribution. To establish
the sensory property, the materials were processed in immunohistochemistry
for calcitonin gene-related peptide.
Results. Many small- to medium-sized neurons were retrogradely labeled L1 a
nd L2 dorsal root ganglia after injection into the sympathetic trunk. The a
nterogradely labeled fibers were found in the dura mater at L4 and L5. Some
of the labeled neurons and fibers were immunoreactive for calcitonin gene-
related peptide.
Conclusion. Sensory fibers from the upper lumbar ganglia innervated the low
er lumbar dura mater directly. These sensory nerves may mediate low back pa
in and possibly interact with sympathetic nerves.